
words = "Python textbook"
vowels = "aeiou"

# find all the vowels in the words string 
all_vowels = [c for c in words if c in vowels]

unique_vowels_set = set(all_vowels)

# Test the code for different 'words' strings
unique_vowels_list = list(unique_vowels_set)
# Modify the result to only show which vowels occur, not every occurrence.
unique_vowels_list.sort()

# Sort the list alphabetically.
print("Unique vowels after deduplication and sorting:", unique_vowels_list)
# Hint: consider the properties of different data structures